Spark plug



Oct. 5, 1943. A. J. HOPKINS SPARK PLUG Filed NOV. 18, 1940 Iwvnvron.

Patented Oct. 5, 1943 UNITED "STATES PATENT OFFICE SPARK PLUG Albert J. Hopkins, Toronto, Ontario, Canada. Application November 18, 1940, Serial No. 366,112

4 Claims.

The invention relates to improvements in spark plugs as described in the present specification and shoun in the accompanying drawing that form a part of the same.

The invention relates generally to spark plugs used in internal combustion engines and more particularly to spark plugs having heating means incorporated therewith for volatizing the vapors in the combustion chamber in readiness for ignition by the spark of the spark plug.

While pre-heating means comprising lengthy heating elements extending through the longitudinal extent of the core, or coiled within the spark plug chamber, have attained some degree of success they have always been slow in heating owing to their great length. Furthermore, such devices have been rendered more or less obsolete with the introduction of the extremely small spark plug now so extensively used and which does not provide space for their accommodation, with the attendant screw parts and contacts.

An important object of the present invention is to provide a spark plug embodying a heating element of extremely short length located almost wholly within the spark plug chamber and which due to its restricted length will commence to diffuse heat instantly upon the transmission of current thereto.

Another object of the invention is to provide simple means for conducting the electric current through the heating element, which will insure positive contact at all times. which will be relatively safe from breakage due to the fact that no screws, terminals or other projecting parts relative to the pre-heating device are carried by the plug and which will not necessitate threading of the plug.

A further object of the invention is to provide a spark plug embodying a heating element of minimum length restricted to the area adjacent the lower end of the electrode, thereby assuring such economy of current as to permit of a great number of plugs being run off a single lead from the control switch.

And generally the objects of the invention are to provide a spark plug of the type specified which will be effective in its purpose of rendering quick and easy the starting of the engine; so constructed that it can be easily assembled and taken apart, and which can be produced at small cost.

The invention consists in the novel features of construction, arrangements and combinations of parts described in the present specification and more particularly pointed out in the claims for novelty following.

In describing the invention reference will be made to the accompanying drawing, in which:

Figure 1 is a side elevation of a spark plug embodying my invention.

Figure 2 is an enlarged central vertical sectional view through the plug, with the heating element shown in full.

Figure 3 is a side elevation of the core, with a portion in vertical section.

Figure 4 is a cross sectional view through the core, taken substantially on the line 44 of Figure 3.

Like numeral; of reference indicate corresponding parts in the various figures.

Referring to the drawing, in the spark plug embodying my invention a is the core, b the shell and c is the threaded sleeve which co-operates with the shell to hold the core in position in the shell.

The core, which can be made of porcelain or any other suitable insulating material, carries the usual electrode 1 which at its top end has an upper terminal connection 2 and at its lower end projects from the lower end of the core for co-operation with the ground electrode 3 carried by the shell. The top end of the core is preferably recessed, as at 4, around the electrode for the admission of a quantity of cement adapted to hold the electrode in position;

The core is shaped to present a cylindrical central body portion 5 tapering to the top end of thecore, as at 6, an annular shoulder I at the lower end of said body, and a tapered lower end 8.

The body portion 5 of the core is cut away at opposite sides to provide diametrically opposed longitudinal grooves 9 and ill extending equal distances from the top of the shoulder 1 to points near where the body starts to taperlto its upper end and these grooves register with cross grooves II and i2 respectively, which latter are cut transversely of the core at opposite sides thereof and extend slightly deeper into the body of the core than do the longitudinal grooves.

A resistance wire l3 constitutes the heating element. This wire is bent in substantially U shape and has its arms l3a extended upwardly through the shoulder I in alignment with the respective grooves 9 and I0 and terminating within the lower ends of said grooves. The heating element is f such lengththat the central U shaped body portion will lie within the chamber H formed in the shell b around the tapered lower end of the core.

The tapered portion 8 of the core is preferably notched, as at l5, to receive the closed portion of the heating element.

The element I3 can be secured to its position by inserting a quantity of cement in one or more openings |5a drilled through the shoulder 1.

Current conductors l6 and I! are mounted in the longitudinal grooves 9 and [0 respectively with their respective lower ends in contact with the ends of the respective arms l3a of the heating element l3. The current conductors l6 and I! each comprise a metal strap of a width to fit the groove in which it is placed and being of the required length to extend across the groove l I, or l2, as the case may be.

l8 and iii are current conductors leading from the source of electrical energy through one plug, or a series of plugs, and providing means for transmitting current through the conductors l6 and I1 and consequently the heating element I3. The conductors i8 and i9 each comprise a metal strap of the required width to slidably fit the transverse grooves II and I2 and of the required thickness to snugly fit the space between the associated longitudinally arranged conductors l6 and i1 and the rear wall of the transverse grooves so as to insure positive contact between the associated transverse and longitudinal conductors.

Strips 20, of rubber, fibre, or other suitable insulating material, are placed within the longitudinal grooves 9 and I!) over the conductors l6 and I! to insure proper insulation of such conductors.

A split ferrule, or sleeve, 2! of metal or other suitable material slidable into position over the top end of the core and adapted to rest on the shoulder 1 provides a means for holding the contacts l6 and I! and their insulators 2|] to their assembled positions.

The threaded sleeve 0 fits over the ferrule 2| and rests on the shoulder while the shell I) has an internally threaded enlarged part 22 adapted to extend over the said shoulder 1 and to thread onto the exteriorly threaded portion of the sleeve 0 whereby to wedge the shoulder I, firmly be tween the end of the sleeve and the annular shoulder 23 provided interiorly of the shell b and thus secure the core to the shell.

In the use of this invention the plugs are screwed into the openings provided in the engine block and the battery wires are connected to the respective terminals 2 in the usual manner. The heating elements of the various plugs are then connected in series by simply sliding the conductors I8 and I 9 through the respective transverse grooves Ii and I2 in the plugs, where they will be in contact with therespective conductors i6 and I1. Through the operation of a suitable switch (not shown in the drawing) current is admitted to the conductors l8 and I9 and passed to the respective longitudinal conductors and thence to the heating elements l3 which, due to their restricted length, instantly difiuse intense heat to the interiors of the shells and the adjacent parts of the combustion chambers, thereby volatizing the vapors for ignition by the spark from the plug when the ignition is turned on.

The present invention provides simple and efficient means for pre-heating the combustion chambers and thereby insuring complete and instant combustion of all gases upon their being ignited by the spark in the usual manner.

What I claim as my invention is:

1. In a spark plug, a shell, a core removably secured in one end of said shell, said core carrying an electrode extending through the open end of said shell, said core having an annular shoulder intermediate its length and disposed within said shell, said core also provided withparallei longitudinal grooves leading upwardly from said shoulder through said shell, a heating element adapted to lie within the shell below said shoulder and having its ends extended through said shoulder in spaced relation to one another and exposed from the top face of said shoulder Within the respective grooves, current conductors lying within said grooves respectively in contact with the respective ends of said heating element, and current conductors in contact with the aforesaid current conductors.

2. In a spark plug, a shell, a core removably secured in one end of said shell, an electrode extending longitudinally through said core and projecting beyond the open end of said shell, said core having an annular shoulder intermediate its length disposed within said shell, said core provided with opposed grooves extending upwardly from said shoulder and terminating a distance above said shell, said core also being provided with opposed transverse grooves registering with the top ends of the respective longitudinal grooves and being of greater depth than said longitudinal grooves, a heating element lying within the shell below said shoulder and having its ends extended through said shoulder and terminating within the respective longitudinal grooves in the core, current conductors lying within the respective longitudinal grooves in contact with the respective ends of said heating element, the said current conductors extending across the adjacent transverse grooves in spaced relation to the rear walls thereof, and current conductors slidable in said transverse grooves behind and in contact with the first mentioned current conductors.

3. In a spark plug, a shell, a core removably secured in one end of said shell, an electrode extending longitudinally through said core and projecting beyond the open end of said shell, said core having an annular shoulder intermediate its length disposed within said shell, said core provided with opposed grooves extending upwardly from said shoulder and terminating a distance above said shell, said core also being provided with opposed transverse grooves registering with the top ends of the respective longitudinal grooves and being of greater depth than said longitudinal grooves, a heating element lying within the shell below said shoulder and having its ends extended through said shoulder and terminating within the respective longitudinal grooves in the core, current conductors lying within the respective longitudinal grooves in contact with the respective ends of said heating element, the said current conductors extending across the adjacent transverse grooves in spaced relation to the rear walls thereof, insulating elements lying in said longitudinal grooves and covering the current conductors therein, current conductors extending through said transverse grooves behind and in contact with the first mentioned current conductors, and a split sleeve encircling the body of the core and holding the current conductors and their insulators to their relative assembled positions.

4, In a spark plug, a core having a central cylindrical body and tapered ends, said body being enlarged at one end to provide an annular shoulder, said body being provided with opposed grooves extending longitudinally from said shouL.

der, said body also being provided with opposed transverse grooves registering with and being of greater depth than said longitudinal grooves, an electrode carried by said core and projecting from the end nearest said annular shoulder, a heating element located in proximity to the projecting end of said electrode and having its ends extended through said shoulder and into the respective longitudinal grooves, current conductors lying within said longitudinal groove in contact with the respective ends of said heating element and entering said transverse grooves, insulators overlying said current conductors within said grooves, a split sleeve encircling the body of the core and holding said current conductors and insulators to their'relative positions, a shell receiving the lower end of said core and said heating element and having an interior shoulder adapted to engage the lower side of the shoulder on the core, and a threaded sleeve encircling the body of the core above the shoulder thereon and adapted to threadingly engage said shell to secure the core to the shell.

ALBERT J. HOPKINS. 

